Electric organ with tremulant effect



y 17, 1966 .1. A. DEREUX ET AL 3,251,925

ELECTRIC ORGAN WITH TREMULANT EFFECT Filed Feb. 12, 1962 2 Sheets-Sheet 1 y 1966 J. A. DEREUX ET AL 3,251,925

ELECTRIC ORGAN WITH TREMULANT EFFECT Filed Feb. 12, 1962 2 Sheets-Sheet 8 Circuits Lp M NH nu J08 United States Patent 3 251 925 ELECTRIC ORGAN WITII TREMULANT EFFECT Jean A. Dereux, 23 Blvd. de Lorraine, Vaires, France, and Jack E. Burchlield, 1005 Chippewa, Buchanan, Mich.

Filed Feb. 12, 1962, Ser. No. 168,404 Claims. (Cl. 84-125) This invention relates generally to electric musical instruments, such as electric organs. More particularly, it relates to means for providing vibrato to the tones produced in an electric instrument having one or more tone generators using rotating members or tone wheels.

In an instrument of this type, the frequency of the tone produced'is determined primarily by the angular velocity of the rotating member of the generator with respect to its associated stator member. To produce a vibrato, the angular velocity of the rotating members is made to increase and decrease periodically about the fundamental velocity at a predetermined modulating frequency, usually between two and ten cycles per second. British Patent No. 656,792 discloses an electric organ utilizing a plurality of tone wheels driven by a single motor With a continuous belt and a vibrato is produced byperiodically varying the rotational speed of the belt. In this patent, the rotation rate of the belt is caused to vary by effectively tightening and loosening the belt periodically to impart a rhythmically varying torque to all of the tone generators simultaneously.

It is an object of the present invention to provide an electric organ utilizing rotating tone member with an improved vibrato.

It is also an object of this invention to provide means for producing a trernulant effect in an electric musical instrument of the type using rotating members, or tone wheels, which does not place mechanical strain on the motor or the torque'transfer drive of the instrument.

More particularly, it is an object of this invention to provide means for producing a tremul'ant effect which periodically varies the angular velocity of the rotating member of each tone generator individually and simultaneously.

Other objects and advantages of this invention will become obvious to-one skilled in the art upon a further study of the drawings and the detailed description to follow.

' the drive pulley. Magnetic means are also provided which cooperate with the resilient connection between the pulley and shaft to produce the periodically varying speed of the shaft and rotating member.

In one type of musical instrument, each tone generator generates the tones of a particular note for all octaves in which that note occurs. The musical instrument therefore has twelve tone generators in order to generate 'all of the 3,251,925 Patented May 17, 1966 tones of the musical scale. It is also an object of the present invention to provide a tremulant effect in an electrical musical instrument of the type using a plurality of rotating tone wheels in which the torque applied to the tone wheels is periodically varied by a single electrically controlled means to produce the tremulant effect.

' In accordance with another embodiment of the present invention, the rotation rate of the tone wheels is varied by periodically changing the torque of the motor driving the tone wheels. Since the tone wheels and the coupling mechanism between the tone wheels and the driving linkage is resonant at the vibrato frequency, variations in torque produced by the motor changes the rotation rate of the driving linkage and these changes are maximized to produce optimum tremulant effect. Also, none of the tone generators require any braking mechanism to produce the desired vibrato, so that only a single control means is required.

Since the frequency of the tones produced is determined by the rotation rate of the tone Wheels, it is essential that the driving motor for the tone wheels have a constant frequency. For this reason, synchronous electric motors have generally :been used. Prior to the present invention, all efforts to vary the speed of the tone wheels at a vibrato rate have operated in spite of the constant rotation rate of the motor. In accordanc with the present invention, the motor is a synchronous electrical motor which operates at a fixed rate of speed, and means are provided to periodically vary the speed of the motor in accordance with the vibrato rate.

Further object-s and advantages of the present inven tion will be readily apparent from a further consideration of this disclosure, particularly when viewed in the light of the accompanying drawings, in which:

FIGURE 1 is a sectional view of one of the generators of an electric organ employing electrostatic type tone generators suitable for use in the present invention;

FIGURE 2 is a fragmentary sectional View of the tone generators of FIGURE 1 taken along the line 22 of FIGURE 1;

FIGURE 3 is a partially diagrammatic view illustrating the tone generator system of the electric organ including the means for producing the tremulant effect;

FIGURE 4 is a schematic electrical circuit diagram of another device for producing the tremulant effect in the electric organ illustrated in FIGURE 3;

FIGURE 5 is a sectional view of one generator of an electric organ employing electrostatic type generators, which constitutes another embodiment of the present invention;

FIGURE 6 is a fragmentary sectional view of the tone generator of FIGURE 5 taken along the line 66 thereof; and

FIGURE 7 is a diagrammatic view illustrating the generator system of the electric organ, utilizing the tone generator of FIGURE 5, including the means for producing the tremul ant effect.

Considering first the embodiment of the invention illustrated in FIGURES 1 through 3, the tone generator illustrated in FIGURE 1 is designated 8 and has a rotatable circular scanner plate 10 fixedly mounted on a shaft 12 within a housing 14. Confronting both sides of the scanner plate lfl are stator plates 16 which, in cooperation with the rotating scanner 10, generate an electric signal representative of a desired musical tone. The signal is conducted from the scanner through a rotating to stationary connection 13, such as a mercury bath connector, to the switching and amplifying circuits of the organ which are well known in the art and diagrammatically indicated at The basic elements of the tone generator here disclosed are those disclosed in the patent to one of the present inventors, Jean A. Dereux, entitled, Electrical Musical Instrument, Patent No. 2,959,083, issued November 8, 1960.

The shaft 12 is journaled within a pair of ball bearings in the housing 14 to make the shaft readily rotatable therein with a minimum of wobble. The shaft 12 extends beyond the housing 14 at the end opposite the mercury connection 18 and has mounted thereon a drive pulley 22. The pulley 22 has a ball bearing 24 centrally fixed therein within which the end of the shaft 12 is secured.

The switching tube 52 is a gas filled thyratron tube and is designed to trigger on the positive peaks of the alternating current output of a vibrato generator 56. The generator 56 is symbolically illustrated in FIGURE 3, and may be a vacuum tube generator or electromechanical generator. The frequency of the vibrato generator 56 is the frequency of the desired vibrato rate, generally between 2 and 10 cycles per second. The thyratron tube 52 has a plate 58 which is connected to the resistor'St), a grid 66, and a cathode or current return electrode 62. The cathode 62 is connected to the terminal 42 of the motor 34, and the grid 60 controls firing of the tube 52. A negative bias voltage is developed across capacitor 64 which is connected in a series circuit with resistors 66 and 68 between The pulley 22 may be rigidly secured to the shaft 12, but A is preferably compliantly mounted thereon. As illustrated in FIGURE 1, the pulley 22 is mounted to the shaft 12 by a spring 26 which resiliently connects it to a disc 28 located coaxially on the shaft between the bearings 20 and 24. The disc 28 is fixedly mounted on and rotatable with the shaft 12. Driving torque is thus applied to the shaft 12 and scanner plate 16 through the spring 26 from the pulley 22 to the disc 28. The spring 26 is a leaf spring anchored at one end to the pulley 22 and at the other end to the disc 28, although a helical spring could be employed but transmits force less linearly. The pulley is rotated by an endless belt 3%, as is shown in FIGURE 3, which also drives other tone generators simultaneously. FIGURE 3 illustrates the tone generators 8 mounted on a mounting plate 32 with the shafts of the tone generators disposed on two parallel planes. Each of the shafts 12 of the tone generators 3 is provided with a pulley 22, and the belt winds about the pulleys 22 to couple all twelve of the tone generators to a single electrical motor 34. The electrical motor 34 is also provided with a pulley 36 I mounted on the shaft thereof which couples the torque of the motor to the belt 30. An idler pulley 38 is disposed at the end of the mounting plate 32 opposite the electric motor 34 to provide the optimum tension for the belt The electric motor 34 is of the synchronous type, and requires two phase electric current. Torque is provided in synchronous electric motors of this type due to the fact that the two electrical currents flowing through the motor have the same frequencies but differ in phase. The first phase current flows through a circuit in the motor connected to the terminals 40 and 42, while the second phase current flows through a circuit in the motor connected to terminals 40 and 44. For the particular construction illustrated, a source of alternating single phase current 46 is connected to the terminals 40 and 42, and the second phase current is achieved by connecting the terminal 42 to the terminal 44 through a capacitor 4% which shifts the phase of the current flowing therethrough. It is thus apparent that the terminal 49 is common to both circuits of the motor.

Vibrato is achieved in the electric organ of FIGURE 3 a by periodically shorting the capacitor 48 through a resistor 50. The resistor 50 is connected in series with a switching tube 52 and a switch 54, and this series circuit is connected in parallel with the capacitor 48. When the switch 54 isclosed, the capacitor 48 is shorted by the resistor 59 during those periods in which the switching tube 52 is conducting. During these periods, the phase of the second phase current provided for the motor 34 is shifted toward the phase of the first current, and therefore the torque of the motor is substantially reduced. As a result, the motor slows down. When the switching tube 52 ceases to conduct, the second phase current resumes its normal phase relation to the first current and restores the torque of the motor 34. The motor 34 therefore accelerates to maintain synchronism with the generator 46.

v The switch 54 permits manual control of vibrato.

the cathode 62 and the grid 60. A resistor 70 is connected in parallel with the capacitor 64. The terminal of the capacitor 64 connected to the cathode 62 is also connected to one terminal of the alternating current source 46, and the other terminal of the capacitor 64 is connected to the other terminal of the alternating current source 46 through a resistor '72 and a diode '74, thereby providing a direct current charge across the capacitor 64. The vibrato generator 56 is connected in parallel with the resistor 66 through a coupling capacitor 76.

FIGURE 4 illustrates a mechanical system for providing vibrato for the electrical organ illustrated in FIGURE 3. In FIGURE 4, the mechanical circuit replaces the power source and switching circuit of FIGURE 3 which are connected to the motor 34, and it is to be noted that the circuit of FIGURE 4 terminates at the terminals 40, 42 and 44 of the motor 34. The alternating current single phase source 46 which provides the basic power for the motor 34 is also illustrated in FIGURE 4 and hasone terminal connected to the terminal 40 of the motor and a second terminal connected to the terminal 42 of the motor 34. The capacitor 48 is also connected between the terminal 42 of the motor :andthe terminal 44- of the motor.

A second synchronous electric motor is electrically connected through a switch 82 to the alternating current source 46, and when the switch is closed, the motor 80 is energized. The motor 80 carries a cam 840m its shaft, and the cam 84 atcuates a movable contact and arm 86. The movable contact and arm 86 confronts a stationary contact 88, and the cam 84 per-iodically'closes the contacts of the contact and arm 86 and stationary contact 88. The stationary contact 88 is connected to one terminal of the capacitor 48, and the contact of the contact and arm 86 is connected to the other terminal of the capacitor 48 through a resistor 90.

When it is desired to provide vibrato for the electric organ, the switch 82 is closed thereby energizing the motor 8i). Rotation of the cam 84 causes the contacts 86 andSS to periodically close at the desired vibrato rate. Upon each closing of the contacts 86 and 88, the capacitor 48 is shorted through the resistor 90, reducing the phase difference between the currents flowing to the motor 34 through the terminals 40 and 42 from those flowing to the motor through the terminals 40 and 44. As a result, the motor loses torque, the tone wheels slow down, and the frequency of the generated signals is reduced. When the cam opensthe contacts 86 and 88, the phase lead established by the capacitor 48 is restored, and the motor regains is torque. The tone wheels are then accelerated to maintain synchronism with the frequency of the alternating current source 46, thereby producing a higher pitch and the desired vibrato. Because of the mechanical resonance achieved between the belt 3% and the tone discs 10, the change in speed of the motor 34 results in a relatively large frequency shift from the tone generator even though relatively little mechanical energy is expended.

If the electrical contacts 86 and 88 are made to close only during those periods when the current flowing through the capacitor 48 is approximately zero, there will be no arcing whatever produced. However, if the current arcing produced. For this reason, the'cam 84 should be positioned on the shaft of the motor 80 to cause closing of the contacts at the proper time, that is, at a time when the current flowing through the capacitor 48 is essentially zero. If this is accomplished, the contacts 86 and 88 will not are and will have an indefinite life. The advantage of the construction of FIGURE 3 over that of FIGURE 4 is that no care need be maintained in manufacturing to properly synchronize the vibrato generator with the alternating current source driving the motor 34. The thyratron tube 52 has a long life in normal usage, and there is no requirement that it fire at the time the current through the capacitor 48 is approximately zero.

It is to be noted that many equivalent devices can be utilized with the present invention. For example, the switching means which provides a shorting link for the capacitor 48 could be utilized to disconnect one of the circuits of the two phase alternating current motor. Further, the synchronous motor may have a direct current supply for one of the circuits therethrough, and the switching means change the phase of the current flowing through the other circuit. Also, rather than use a generator 56 in the device illustrated in FIGURE 3, an electrical motor, such as 80 of FIGURE 4, could be utilized.

A further embodiment of the present invention is illustrated in FIGURES 5 through 7. In this embodiment, the tone generator is designated 108 and has a rotatable circular scanner plate 110 fixedly mounted on a shaft 112 within a housing 114. Confronting thescanner plate 110 on either side are stator plates 116 which, in cooperation with the rotating scanner 111), generate an electric signal representative of a desired musical tone. The signal is conducted from the scanner through a rotating to stationary connection 118, such as a mercury bath connector, to the switching and amplifying circuits of the organ which are well known in the art and diagrammatically indicated at 119.

The shaft 112 is journaled within a pair of ball bearings 120 in the housing 114 to make the shaft readily rotatable therein with a minimum of wobble. The shaft 112 extends beyond the housing 114 at the end opposite the mercury connection and has mounted thereon a drive pulley 122. The pulley 122 has a ball bearing 124 centrally fixed therein within which is journalled the end of the shaft'112. The pulley 122 may be rigidly secured to the shaft 112, but is preferably compliantly mounted thereon. As illustrated in FIGURE 5, the pulley 122 is mounted to the shaft 112 by a spring 126 which resiliently connects it to the base 127 of a disc 128 which is fixedly mounted on and rotatable with the shaft 112. Driving torque is thus applied to the shaft 112 and scanner plate 110 through the spring 126 from the pulley 122.- The spring 126 is a leaf spring anchored at one end to the pulley 122 and at the other end to the base 127, although a helical spring could be employed but transmits force less linearly. The pulley is rotated by an endless belt 138 as is shown in FIGURE 6 which also drives other tone generators simultaneously.

When the pulley 122 is driven by a belt, it may be fixedly mounted on the shaft 112 and the resilience of the belt and variations in the tension employed to produce vibrato. With the resilient coupling here employed, a friction or direct'drive may be used for the tone generators also.

The disc 128 is fabricated of an electrically conducting nonmagnetic material and is rotatably driven Within a gap 130 in a stationary magnetic circuit 131. The magnetic circuit 131, comprises a ferromagnetic core 132 which is closed except for the gap 130 and surrounded by a coil or winding 134. When a magnetic flux is passed across the gap 131 eddy currents are generated within the rotating disc 128. The eddy currents are directed around closed paths within the disc so that the magnetic fields set up by the eddy currents oppose the magnetic flux 6 across the gap 130. This produces a drag on the disc 128. The drag on the disc 128 causes the shaft 112 and scanner plate to momentarily lag behind the pulley 122 by a maximum angle a, illustrated in FIGURE 6.

The rotatable mounting of the pulley 122 on the shaft 112 and the resilient spring 126 therebetween provide most of the compliance required to achieve this angle. When the magnetic flux is removed, the spring 126 causes the scanner plate and shaft to return to its original relative angular position and to overshoot that position. If a periodic electric current of the desired tremulant frequency, preferably 6 cycles per second, is applied to the coil 134, the drag will cause the angular velocity of the shaft and scanner plate to oscillate about the fundamental angular velocity of the drive pulley to produce a tremulant variation in the generated tone.

It is to be noted that the connecting spring 126 and the rotational mass of the scanner plate 110, shaft 112, and conductive disc 128 may be made resonant at the desired tremulant frequency, which will increase efliciency and reduce the power required to sustain oscillation. The ball bearings 121) and 124 reduce the dissipation materially and increase the mechanical resonance Q factor, i.e., 211' times the ratio of the energy stored in the device to the energy dissipated in the device in one cycle. Some dissipation, however, is necessary because the tremulant effect might be energized by slight irregularities in the drive system even though the coil is not being energized by a generating signal. A Q of between 10 and 20 is therefore preferable. It is to be noted that optimum results are achieved for the constructions of FIGURES 1 through 4 also with a Q between 10 and 20.

In FIGURE 7, a system is diagrammatically shown comprising twelve tone generators 108 driven from a single motor 136 by the endless belt 138. Each tone generator 108 produces all octaves within the range of the instrument of one particular note of the musical scale. Since the player may select a plurality of notes to be played simultaneously, it is desirable that the vibrato superimposed on each note he at a rate proportional to frequency and in fixed phase relationship with one another for the desired musical effects. Therefore, the coils 134 of all the generators 108 are connected in series with an alternating current source 142 and a switch 144. The switch 144 permits the player of the electric organ to energize the vibrato system to produce the music he desires. A variable resistor 146 is also provided to control the amplitude of the vibrato in accordance with the desires of the musician. It is also to be noted that variable resistors 147 are connected in parallel with one or more of the coils 134 to facilitate the initial tuning of the vibrato and achieve proper balance. This type of tremulant tuning is not available in instruments in which the tremulant effect is produced in the motor or the drive system. It is also to be understood'that the coils 134 may be connected in parallel with the alternating current source, however, the impedance to which the source 142 should be matched is substantially lower than with the coils in series.

The present invention can clearly .be used with all types of tone wheels, whether electrostatic, electromagnetic, or photoelectric, and can the used whether a plurality of tone generators are utilized or but a single tone generator. f It is therefore intended that the scope of the present invention .be not limited by the foregoing disclosure, but rat-her only by the appended claims.

The invention claimed is:

1. An electric organ for producing vibrato at a given frequency comprising, in combination: a tone generator having a shaft, a tone wheel mounted on the shaft, a synchronous electric motor having two electrical circuits therein adapted tobe energized by two electrical currents of the same frequency differing in phase, and a cornpliant coupling means mechanically connected between the mass of the tone wheel and shaft producing mechanical resonance in the tone generator at the vibrato frequency; means for electrically connecting the circuits of the motor to a source of single phase alternating current including a phase shifting element in series with one of the circuits of the motor, and means for periodically reducing the phase difference of the currents flowing in the two circuits of the motor at the same frequency as the frequency of mechanical resonance of the tone generator.

2. A device for electrically producing musical tones comprising a shaft, a variable capacitor having a rotatable scanner plate fixedly mounted on said shaft and a stator, a pulley rotatably mounted on said shaft and resiliently connected thereto, the mass of the rotatable system including the scanner plate and shaft and the resilence of the coupling being mechanically resonant at a frequency between 2 and 10 cycles per seconds, means for driving said pulley and thereby said shaft and scanner plate at a constant angular velocity, an electrically conducting disc fixedly mounted on said shaft, means for periodically conducting magnetic flux through said disc at a rate approximately equal to the frequency of mechanical resonance of the rotatable system, and an electric circuit containing said variable capacitance for producing an electric signal representative of a tremulant musical tone.

3. A device for electrically producing musical tones comprising a shaft, a variable capacitance having a rotatable scanner plate fixedly mounted on said shaft and a stator, a pulley having a ball type bearing within which said shaft is journaled, a spring having one end fixed to said pulley and the other end fixed to said shaft, the mass of the rotatable system including the shaft and rotatable scanner plate and the compliance of the spring producing a mechanical resonance with a frequency between 2 and 10 cycles per second, means for driving said pulley and thereby said shaft and scanner plate at a constant angular velocity, an electrically conducting disc fixedly mounted on said shaft, an electromagnet having its pole ends adjacent one another on opposite sides of said disc, means for periodically energizing said electroma-gnet at the frequency of mechanical resonance of the rotatable system, and an electric circuit containing said variable capacitance for producing an electric signal representative of a tremulant musical tone.

4. A device for electrically producing musical tones comprising a shaft, a variable capacitance having a rotatable scanner plate fixedly mounted on said shaft and a stator, a pulley having a ball type bearing within which said shaft is journaled, a leaf spring having one end fixed to said pulley and the other end fixed to said shaft, means for driving said pulley and thereby said shaft and scanner plate at a desired angular velocity, an electrically conducting disc fixedly mounted on said shaft, said shaft, scanner plate, disc and spring being resonant at a frequency between 2 and 10 cycles per second and a mechanical resonance Q factor of between 10 and 20, an electromagnet having its pole ends adjacent one another on opposite sides of said disc, means for energizing said electromagnet at a frequency between 2 and 10 cycles per second, and an electric circuit containing said variable capacitance for producing an electric signal representative of a tremulant music tone.

5. An electric musical instrument comprising a plurality of variable capacitances each having a rotatable scanner plate and a stator, an equal plurality of shafts each fixedly mounting one of said scanner plates, an equal plurality of pulleys, each of said pulleys having a ball type bearing within which one of said shafts is journaled, an equal plu rality of springs each having one end fixed to a pulley and its other end fixed to its associated shaft, each of said springs and its associated shaft and rotatable scanner plate forming a rotatable mechanical system having a mechanical frequency of resonance. between 2 and 10 cycles per second, means for driving each of said pulleys and thereby its associated shaft and scanner plate at a constant angular velocity, an electrically conducting disc fixedly mounted on each shaft, stationary means for periodically passing a-magnetic flux through each of said discs simultaneously at the mechanical frequency of resonance thereof, and an electric circuit electrically connected to each of said variable capacitances for producing electric signals representative of tremulant musical tones.

6. An electric musical instrument comprising a plurality of variable capacitances each having a rotatable scanner plate and a stator, an equal plurality of shafts each fixedly mounting one of said scanner plates, an equal plurality of pulleys each having a ball type bearing within which one of said shafts is journaled, an equal plurality of leaf springs each having one end fixed to a pulley and its other end connected to its associated shaft, each assembly of a shaft, scanner plate and spring being resonant at between 2 and 10 cycles per second and having a mechanical resonance Q of between 10 and 20, means for driving each of said pulleys and thereby its vassociated shaft and scanner plate at a constant angular velocity, an electrically conducting disc fixedly mounted on each shaft, an equal plurality of electromagnets each having its pole end-s adjacent one another on opposite sides of one of said discs, means serially connecting the electromagnets for electrically energizing each of said electromagnets simultaneously at a frequency between 2 and 10 cycles per second, and an electric circuit electrically connected to each of said variable capacitances for producing electric signals representative of tremulant musical tones.

7. An electric organ for producing vibrato at a constant frequency comprising, in combination: a tone generator having a shaft, a tone wheel mounted on the shaft, a synchronous electrical motor, a pulley rotatably mounted on the shaft and mechanically coupled to the motor, resilient coupling means mounted between the pulley and the shaft for rotating the shaft at an average rate equal to that of the pulley, the resilience of said means and the effective mass of the rotatable system formed by the shaft and tone wheel producing a mechanical resonance at approximately the vibrato frequency, and means for periodically producing a rotational torque between the pulley and the shaft at said vibrato frequency, thereby periodically stressing the resilient coupling means at the mechanical frequencyof resonance of the rotatable system, whereby the rotation rate of the tone wheel will be periodically varied between overspeed and underspeed.

8. An electric organ for producing vibrato at a given frequency comprising the elements of claim 1 wherein the means for periodically reducing the phase difference of the currents flowing in the two circuits of the motor at the same frequency as the frequency of mechanical resonance of the tone generator comprises means for electrically connecting the two circuits of the motor to a source of single phase alternating current including a capacitor connected in series with one of the circuits of said motor, and means for shorting said capacitor comprising a periodic switching means and a resistor connected in series across the capacitor.

9. An electric organ comprising the elements of claim 8 wherein the switching means comprises a second synchronous electric motor connected in parallel with the first electric motor, and a switch mechanism mechanically coupled to the electric motor having a pair of contacts which make and break in response to operation of the motor.

10. An electric organ comprising the elements of claim 8 wherein the switch mechanism comprises a switching tube having a control grid, plate and current return electrode, the plate and current return electrode being connected in a series circuit with the resistor, and the series circuit being connected across the capacitor, an alternating current vibrato generator connected in series between the control grid and the current return electrode,

and means biasing the control grid relative to the current return electrode to limit conduction of the switching tube to periods of positive output from the vibrato generator.

References Cited by the Examiner UNITED STATES PATENTS 1,956,350 4/1934 Hammond 84-1.17 11,991,727 2/1935 Brimberg 84 1.25 X 2,513,109 6/1950 Roth 84-1:1=8

Reeves 318220.2 Williams 84-125 Dereux 84--1.28 Schwartz et a1. 84-1425 Gibbs 84--1.28 X

GEORGE N. WESTBY, Primary Examiner. ARTHUR GAUSS, Examiner.

E. DREYFUS, Assistant Examiner. 

1. AN ELECTRIC ORGAN FOR PRODUCING VIBRATO AT A GIVEN FREQUENCY COMPRISING, IN COMBINATION: A TONE GENERATOR HAVING A SHAFT, A TONE WHEEL MOUNTED ON THE SHAFT, A SYNCHRONOUS ELECTRIC MOTOR HAVING TWO ELECTRICAL CIRCUITS THEREIN ADAPTED TO BE ENERGIZED BY TWO ELECTRICAL CIRCUITS OF THE SAME FREQUENCY DIFFERING IN PHASE, AND A COMPLIANT COUPLING MEANS MECHANICALLY CONNECTED BETWEEN THE MASS OF THE TONE WHEEL AND SHAFT PRODUCING MECHANICAL RESONANCE IN THE TONE GENERATOR AT THE VIBRATO FREQUENCY; MEANS FOR ELECTRICALLY CONNECTING THE CIRCUITS OF THE MOTOR TO A SOURCE OF SINGLE PHASE ALTERNATING CURRENT INCLUDING A PHASE SHIFTING ELEMENT IN SERIES WITH ONE OF THE CIRCUITS OF THE MOTOR, AND MEANS FOR PERIODICALLY REDUCING THE PHASE DIFFERENCE OF THE CURRENTS FLOWING IN THE TWO CIRCUITS OF THE MOTOR AT THE SAME FREQUENCY AS THE FREQUENCY OF MECHANICAL RESONANCE OF THE TONE GENERATOR. 